1. Field of the Invention
The present invention relates generally to a gas turbine engine, and more specifically to a turbine stator vane with a purge air hole for an inter-stage seal housing.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In a gas turbine engine, such as a large frame heavy-duty industrial gas turbine (IGT) engine, a hot gas stream generated in a combustor is passed through a turbine to produce mechanical work. The turbine includes one or more rows or stages of stator vanes and rotor blades that react with the hot gas stream in a progressively decreasing temperature. The efficiency of the turbine—and therefore the engine—can be increased by passing a higher temperature gas stream into the turbine. However, the turbine inlet temperature is limited to the material properties of the turbine, especially the first stage vanes and blades, and an amount of cooling capability for these first stage airfoils.
The first stage rotor blade and stator vanes are exposed to the highest gas stream temperatures, with the temperature gradually decreasing as the gas stream passes through the turbine stages. The first and second stage airfoils (blades and vanes) must be cooled by passing cooling air through internal cooling passages and discharging the cooling air through film cooling holes to provide a blanket layer of cooling air to protect the hot metal surface from the hot gas stream.
A turbine stator vane will include an internal cooling air circuit to provide cooling for the airfoil and the endwalls as well as a forward and an aft purge air hole to provide purge air to an inter-stage seal housing and an aft rim cavity. FIG. 4 shows a prior art stator vane with a number of bleed of holes located at an end of the leading edge serpentine flow channel that provides purge air for inter-stage seal housing (ISSH). FIG. 5 shows a prior art stator vane with a purge air hole located at a bottom of the inner diameter root turn. In both of these prior art designs, the air used to purge the ISSH is hot air that travels along the leading edge region of the airfoil which is the hotte4st surface of the airfoil.